Method of making heater units



Sept. 11, 1928. 1 1,684,184 w. R. KING- METHOD OF MAKING HEATER UNITS Filed Feb. 1, 1927 Fig.4

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ilil lili WITNESSES: INVENTOR William E. King.

Patented Sept. 11, 1928. I -UNITED STATES 1,684,184 PATENT OFFICE.

WILLIAE 3. KING, OF MANSFIELD, OHIO, ASSIGNOR '10 WESTINGHOUSE ELECTRIC &

MANUFACTURING COMPANY, A CORPORATION or PENNSYLVANIA.

METHOD OF MAKING HEATER UNITS.

Application filed February 1, 1927. Serial No. 165,126.

My invention .relates to electric heating units'and particularly to tubular or cartridge heating units and to methods of making the same.

An object of my invention is to provide a. highly efiicient, compact and easily manufactured tubular heating unit.

Another object is to provide a heating unit of the cartridge or tubular type that shall embody expansively oxidized electric-insulating material for holding the resistor and a terminal rod in proper operative position within a metal casmg.

In practicing my invention, I provide a helically wound resistor wire having a terminal rod located therein and electrically connected thereto at one end thereof, a solid mass of initially metallic magnesium that has been expansively oxidized to magnesium hydroxide and magnesium oxide holding the rod within the helix and the helix within a tubular metallic casing. Bushings of electric msulating material are provided at the ends of the tubular casing.

In the single sheet of drawings:

Fig. 1 is a view, in longitudlnalsectmn of a completed heating unit embodying my 1n- 'vention,

Fig. 2 is a view, in lateral section taken on the line 11-11 of Fig. 1,

Fig. 3 is an end view of the heating unit,

Fig. 4 is a view, partially in side elevation and partially in section, of an outer helix of metallic magnesium,

Fig. 5 is a view, partially in side elevation and partially in section, of an inner helix of metallic magnesium, and,

Fig. 6 is a view, in side elevat1on, of certain parts ofa device embodying my invention, shown in assembled relation.

An electric heating unit 11 of the cartridge or tubular type comprises a tubular metal casing 12 having located there n. an open helix of resistor'wire13 (see Flg'. 6) together with a terminal rod 14 that is substantially co-axial with the helix 13. One end of the resistor wire is wound tightly around the corresponding end of the rod 14 in order to provide a good electrical connection between the rod and the resistor Wire. The rod 14 is not straight but is made. slightly crooked or wavy, as shownin Figs. 1 and 6 of the drawings, for a purpose to be herein- -a,fter describedf An open helix 15, made from a strlp of metallic magnesium, is located around the rod 14 and within the helix 13, and-an open helix 16 of magnesium strip, made in substantlally the same manner as the helix 15, is located around the outside of the helix 13. A bush ng 17 of a suitable electric insulatmg mater1al is located on the forward end of the rod 14, the rod being slightly deformed in order to bend it away from the co-axial position with the coil 13, as shown more partlcularly in Fig. 6 of the drawing. A bushmg 13 of some suitable electric-insulating material is provided and has a plurality of.

openings therethrough to receive the forwardhelix 13 of resistor wire, the outer helix 16 of metallic magnesium and the bushing 17 may then be located within the tubular member 12 in which they fit loosely. The bushing 18 need not be located on the rod 14 at this stage of the manufacture but may be located in its proper operative position later.

The tubular element 12 and the other members located therein, as described above, are then placed within a closed casing usually! called an autoclave, in which. the assembled heating unit is subjected, for a predetermined length of time, to the action of high-pressure and high-temperature steam in accordance with the process disclosed and claimed in Backer reissued Patent N 0. 16,340. The method comprises the use of steam at pressures of 100 pounds per square inch and above, and the treatment is continued until all of the initial metallic magnesium has been I transformed into a crystalline structure of magnesium hydroxide or magnesium oxide whlch is an electric nonconductor and is also 100 a good conductor of heat.

The initially metallic magnesium tends to expand to substantially 200% of its initial volume when changed into magnesium hydroxide or oxide, and, if such additional space 105 or volume is not available, a compacting action will take place whereb the rod 14 will be clamped or held tight y within the helix 13 and the helix 13 will be held tightly within the conduit or tubular casing 12. If

The compacted electric-insulating and heatconducting crystalline mass of magnesium :hydroxide or oxide thus produced provides a highly eiiicient path for the flow of heat from the energized resistor 13 outwardly to the casing 12.

After the above described heat and oxidizing treatment has been completed, the bushing 18 may be located in the end of the casing 12, the wire end connected to the terminal member 19 and the end of the casing 12 spun over, as indicated at 21 in Fig. 1 of the drawing. A closure 22, comprising a bushing of electric-insulating material, is located at the other end of the casing 12, the end portion thereof being spun over the bushing 22, substantially as shown in the drawing.

The device embodying my invention thus provides a relatively simple and easily manufactured heating unit of the cartridge type having expansively oxidized crystalline electric-insulating material in the casing for holding all of the parts, including a terminal rod, in proper operative positions relatively to each other therein, and for providing a highly efiicient heat path from the resistor to the casing.

Various modifications may be made in the device embodying my inventon without de-- parting from the spirit and scope thereof, and I desire that only such limitations shall be placed thereon as are imposed by the prior art or are specifically set forth in the appended claims.

I claim as my invention:

1. The method of making a tubular heating unit which comprises winding a resistor wire into helical form, locating within the helix a terminal rod one end of which is electrically connected to the corresponding end of the resistor wire, locating on the terminal rod and within the helix an open helix of a strip of metallic magnesium, locating an open helix of a strip of metallic magnesium around said helix, placing the helix, terminal rod and two helices of magnesium loosely within a tubular metal casing, and then subjectin the parts thus assembled to the action of igli pressure steam in a container to expansively oxidize the metallic magnesium into a or stalline mass of electric insulating materi 2. The method of making a tubular heatin unit, which comprises locating a terminal r0 within a helically wound resistor wire, electrically connecting one end of the resistor to the corresponding end of the terminalrod locating a loosely wound helix of a strip oi metallic magnesium between the rod and the resistor wire, locating a second loosely wound helix of a strip of metallic magnesium around the resistor wire, placing the assembled parts in a tubular metallic casing, subjecting these parts to the action of high pressure steam in a closed container until the magnesium has been expansively oxidized into a solid crystalline mass of electric-insulating magnesium hydroxide and magnesium oxide, and then closing the ends of the casin with bushings of electric-insulating materisfi.

In testimony whereof, I have hereunto sub scribed my name this 25 day of Jan. 1927. WILLIAM R. KING. 

